NEW YORK
— Looking down from 6,500 feet above Boston, the East Coast spreads out sparkling in the night. A second later, the plane hits a cloud bank and there's nothing but dark gray - visibility zero. "As a pilot, you're trained to think about everything that can go wrong," says Victor Antonini, dropping his twin engine Cessna 310 a thousand feet below the clouds.

Even with five navigational devices lit up on his dashboard, Mr. Antonini says that in unfamiliar mountainous terrain on a cloudy day or night, it's easy for a pilot to become disoriented.

Such momentary lapses are one factor responsible for the leading cause of airline fatalities. It's called controlled flight into terrain (CFIT), and it's a top priority of aviation safety experts around the world. Pilots simply get confused about their whereabouts and inadvertently fly into a mountainside or embankment. "It's the biggest problem in aviation today," says Stuart Matthews, president of the Flight Safety Foundation (FSF), a nonprofit Virginia-based group.

Stuart and other aviation experts see all the earmarks of CFIT in the devastation left behind after Cebu Pacific Air flight 387 slammed into the side of a mountain in the Philippines Monday. It is adding a new sense of urgency to a problem the industry has been wrestling with for years.

In 1992, the FSF organized an international task force to identify the causes of CFIT and find ways to eliminate it. Their goal: to cut such accidents worldwide by 50 percent in five years. With a massive international education and training effort still under way, there's been mixed success.

In 1997, CFIT accidents were responsible for 640 fatalities, a record. But only seven accidents were attributed to CFIT - down from 20 in 1992. "The figures seem to indicate it's working," says Mr. Matthews. "Although there's far more flying than five years ago, we've got distinctly fewer CFIT accidents."

The primary cause of CFIT is simple human error: Pilots lose what's called "situational awareness." They could be in a cloud bank and misread their instruments, or misunderstand an air traffic controller's direction. Or, while in the process of reading a chart or programming a piece of equipment, they stop monitoring the plane's altitude for a few critical seconds.

"We recognize that technology is eventually going to defeat CFIT," says Matthews. "But it's going to take some time to implement enhanced ground proximity warning systems (GPWS) in every airplane."

GPWS technology senses when a plane gets too close to the ground and alerts the pilots. It is mandatory equipment in commercial aircraft in the US. But most are equipped with older systems that give pilots only 30 to 40 seconds to avert a disaster. In many cases, that's not enough. Engineers have developed an enhanced system, but it could take 20 years before it's installed in every commercial jet.

General aviation aircraft, the private and corporate planes like Mr. Antonini's Cessna that do most of the flying in the US, aren't required to carry GPWS. It's too expensive. That makes training to prevent CFIT a high priority, says Matthews.

But pilots aren't the only ones responsible for CFIT accidents. A study done for the International Civil Aviation Organization found that 88 percent of 24 CFIT accidents between 1984 and 1994 had root causes in "organizational processes" - things like lack of pilot training and poor scheduling.

But between the current global effort to defeat CFIT and advances in technology, experts are confident that, in the future, they will face fewer scenes like the tragic one in the Philippines.